CriticalCVE-2025-14847

    Zlib compressed protocol header length confusion may allow memory read (CVE-2025-14847)

    Published In CISA KEV since Sources: SingCERT, pwn.watch, CVE.org, OSV

    What is affected, what to do

    Mismatched length fields in Zlib compressed protocol headers may allow a read of uninitialized heap memory by an unauthenticated client. This issue affects all MongoDB Server v7.0 prior to 7.0.28 versions, MongoDB Server v8.0 versions prior to 8.0.17, MongoDB Server v8.2 versions prior to 8.2.3, MongoDB Server v6.0 versions prior to 6.0.27, MongoDB Server v5.0 versions prior to 5.0.32, MongoDB Server v4.4 versions prior to 4.4.30, MongoDB Server v4.2 versions greater than or equal to 4.2.0, MongoDB Server v4.0 versions greater than or equal to 4.0.0, and MongoDB Server v3.6 versions greater than or equal to 3.6.0.

    The vulnerability is being actively exploited; treat it as a priority. Update MongoDB Server to version 8.2.3, MongoDB Server to version 8.0.17, MongoDB Server to version 7.0.28. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • MongoDB Server lt 8.2..8.2.3
    • MongoDB Server lt 8.0..8.0.17
    • MongoDB Server lt 7.0..7.0.28
    • MongoDB Server lt 6.0..6.0.27
    • MongoDB Server lt 5.0..5.0.32
    • MongoDB Server lt 4.4..4.4.30
    • MongoDB Server eq 4.2..4.2
    • MongoDB Server eq 4.0..4.0
    • MongoDB Server eq 3.6..3.6
    Fixed in
    • MongoDB Server 8.2.3
    • MongoDB Server 8.0.17
    • MongoDB Server 7.0.28
    • MongoDB Server 6.0.27
    • MongoDB Server 5.0.32
    • MongoDB Server 4.4.30

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.7

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v4

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: SingCERT, pwn.watch, CVE.org, OSV

    83.2 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.68

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    235.84 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab), CSA/SingCERT How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.7 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.5
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.7
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    83.2 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    99.68
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 30 December 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-130

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is network-reachable, needs no authentication or user interaction, and has low attack complexity. It ranks among the CVEs most likely to be exploited, and exploit tooling is publicly available. Attackers mass-scan for reachable MongoDB instances and repeatedly scrape heap fragments to harvest credentials and data. The integrity and availability impact usually follows as a second stage, for example data theft or extortion via wiped databases; CISA does not currently flag ransomware use. Score internet-facing instances and EOL versions (3.6–4.2) as critical and fix them immediately. Internally segmented instances are high priority for the regular emergency patch window, including precautionary credential rotation.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Find exposed instances: Inventory every MongoDB server with a reachable mongod/mongos port (default TCP 27017, plus 27018/27019 for shards and config servers). Handle internet-facing instances and those reachable from untrusted segments first. Exploitation happens pre-authentication, so having access control enabled does not protect you.
      • Patch: Upgrade to the fixed releases: 8.2.3, 8.0.17, 7.0.28, 6.0.27, 5.0.32 or 4.4.30. Roll replica sets one member at a time: secondaries first, then rs.stepDown(), then the former primary.
      • EOL branches with no fix: MongoDB 4.2, 4.0 and 3.6 will not receive a patch. Isolate these instances from the network or disable zlib immediately (see below), and schedule migration to a supported branch.
      • Interim workaround: Disable zlib network compression. Set net.compression.compressors: snappy,zstd (or disabled) in mongod.conf, or start with --networkMessageCompressors snappy,zstd. A restart is required.
      • Rotate secrets: The flaw leaks uninitialised heap memory, which can contain passwords, SCRAM material, session data, connection strings and document contents. On any exposed instance, proactively rotate database user passwords, application credentials and, where relevant, keyfile or x.509 material.
      • Check regulatory clocks: If there are signs of exploitation, assume confidential or personal data may have leaked. Hand the NIS2 early-warning deadline (24 h) and the GDPR Art. 33 notification window (72 h) to incident management.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Block TCP 27017–27019 at the perimeter and between zones. Allow access only from defined application subnets. Restrict net.bindIp to internal interfaces and never bind 0.0.0.0 on a publicly reachable host.
      • IPS rule (Suricata/Snort): Alert on or drop MongoDB OP_COMPRESSED messages (opCode 2012, little-endian |dc 07 00 00| at offset 12) with compressorId 2 (zlib, byte at offset 24) from external sources. Example: alert tcp $EXTERNAL_NET any -> $HOME_NET 27017 (msg:"MongoDB OP_COMPRESSED zlib from external - CVE-2025-14847"; flow:to_server,established; content:"|dc 07 00 00|"; offset:12; depth:4; byte_test:1,=,2,24; threshold:type both,track by_src,count 20,seconds 60; sid:9001484701; rev:1;)
      • Configuration hardening: Align the compressor list across all nodes and clients (compressors=snappy,zstd in the connection string). This avoids negotiation surprises once zlib is removed.
      • Connection throttling: Exploitation relies on many short connections to harvest memory fragments. Cap net.maxIncomingConnections and rate-limit new connections per source IP at the host firewall (e.g. nftables with ct count/limit rate).
      • Least privilege / blast-radius reduction: Scope application accounts to the databases they need and issue separate credentials per application, so any leaked fragment has limited value. Requiring TLS with client certificates further shrinks the attack surface from foreign networks.

    3. Runbook step 3

      Detection rules

      • MongoDB structured log (4.4+): Look for bursts of "id":22943 (connection accepted) from one source IP with no matching "id":51800 (client metadata) and a rapid "id":22944 (connection ended). Legitimate drivers always send client metadata. SPL sketch: index=mongodb (id=22943 OR id=51800) | stats count(eval(id=22943)) as conn count(eval(id=51800)) as meta by remote_ip | where conn>100 AND meta<conn*0.1
      • Network telemetry (Zeek conn.log / NetFlow): High volumes of short-lived TCP sessions to 27017 from a single external source. A telltale sign is a byte asymmetry: small requests with comparatively large responses. Pattern: id.resp_p == 27017 and duration < 1s, grouped by id.orig_h with a per-minute threshold.
      • Suricata alerts: Hits on the OP_COMPRESSED/zlib signature above from sources outside the application subnets. Treat any external hit as an incident.
      • Post-leak follow-on activity: Review successful authentications ("id":5286306, "Successfully authenticated") from unfamiliar IPs or unusual users. Also flag listDatabases, bulk reads or dropDatabase commands shortly after a suspicious connection burst.
      • Asset reconciliation: Compare external scan views (attack surface management, Shodan queries on your own ranges) against the CMDB. Treat any MongoDB instance that is not inventoried as shadow IT.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Mismatched length fields in Zlib compressed protocol headers may allow a read of uninitialized heap memory by an unauthenticated client. This issue affects all MongoDB Server v7.0 prior to 7.0.28 versions, MongoDB Server v8.0 versions prior to 8.0.17, MongoDB Server v8.2 versions prior to 8.2.3, MongoDB Server v6.0 versions prior to 6.0.27, MongoDB Server v5.0 versions prior to 5.0.32, MongoDB Server v4.4 versions prior to 4.4.30, MongoDB Server v4.2 versions greater than or equal to 4.2.0, MongoDB Server v4.0 versions greater than or equal to 4.0.0, and MongoDB Server v3.6 versions greater than or equal to 3.6.0.

    Source: CSA/SingCERT, pwn.watch, NVD (NIST), cvelistv5, CISA KEV Catalog, OSV (Open Source Vulnerabilities), CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    MongoDB Inc.MongoDB Server
    • 4.2
    • 6.0 – < 6.0.27
    • 4.4 – < 4.4.30
    • 7.0 – < 7.0.28
    • 4.0
    • 3.6
    • 5.0 – < 5.0.32
    • 8.0 – < 8.0.17
    • 8.2 – < 8.2.3
    • —
    • 6.0.27
    • 4.4.30
    • 7.0.28
    • —
    • —
    • 5.0.32
    • 8.0.17
    • 8.2.3
    mongodbmongodb
    • 3.6.0 – < 4.4.30
    • 8.0.0 – < 8.0.17
    • 6.0.0 – < 6.0.27
    • 7.0.0 – < 7.0.28
    • 5.0.0 – < 5.0.32
    • 8.2.0 – < 8.2.3
    • 4.4.30
    • 8.0.17
    • 6.0.27
    • 7.0.28
    • 5.0.32
    • 8.2.3
    Distribution and container packages (6)

    Downstream packages (e.g. Bitnami, Debian, Ubuntu, Red Hat). Versions refer to the distribution, not the vendor.

    Distribution and container packages
    Affected versionsFixed in
    bitnamimongodb
    • 4.4.0
    • 6.0.0
    • 7.0.0
    • 8.0.0
    • 8.2.0
    • 5.0.0
    • —
    • —
    • —
    • —
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-130Improper Handling of Length Parameter Inconsistency

      Base

      The product parses a formatted message or structure, but it does not handle or incorrectly handles a length field that is inconsistent with the actual length of the associated data.

      Entry at MITRE CWE-130

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    CSA/SingCERTHigh Severity Vulnerability in MongoDB Server (opens in a new tab)CSA/SingCERTactively exploited
    PoC-in-GitHub (nomi-sec)CVE-2025-14847-mongobleed (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • jira.mongodb.orgSERVER-115508web, Issue tracking, Patch, Vendor advisory, pwn-watch
    • openwall.comlists/oss-security/2025/12/29/21web, Mailing list
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-14847web, government-resource, Third-party advisory, US government resource
    • NVD (NIST)vuln/detail/CVE-2025-7259web
    • vicarius.iovsociety/posts/cve-2025-14847-detection-script-heap-memory-expo…Exploit, Third-party advisory
    • vicarius.iovsociety/posts/cve-2025-14847-mitigation-script-heap-memory-exp…Exploit, Third-party advisory
    • smartkeyss.compost/mongobleed-pre-auth-memory-disclosure-via-op_compressed-in…Technical description, Third-party advisory
    • pwn.watchpwn.watch: MongoBleed: pre-auth heap memory leak in MongoDB Serverpwn-watch
    • cyber.gc.caAL25-021 - Vulnerability affecting MongoDB - CVE-2025-14847pwn-watch
    • unit42.paloaltonetworks.comThreat Brief: MongoDB Vulnerability (CVE-2025-14847)pwn-watch
    • openwall.comoss-security: MongoBleed CVE-2025-14847pwn-watch
    • NVD (NIST)NVD: CVE-2025-14847pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2025-14847
    <a href="https://intel.neosec.eu/en/cve/CVE-2025-14847"><img src="https://intel.neosec.eu/badge/cve/CVE-2025-14847.svg?lang=en" alt="CVE-2025-14847 – NEOSEC Intel" height="20"></a>