Pnggroup Libpng: Use After Free (CVE-2026-34757)
Published Last modified Sources: SUSE, Ubuntu, BSI, CVE.org, Debian LTS, Red Hat, Debian, Msrc Update Guide, EUVD
What is affected, what to do
LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. From 1.0.9 to before 1.6.57, passing a pointer obtained from png_get_PLTE, png_get_tRNS, or png_get_hIST back into the corresponding setter on the same png_struct/png_info pair causes the setter to read from freed memory and copy its contents into the replacement buffer.
An exploit is publicly available. Update libpng to version 1.6.57, libpng Trunk to version 1.8.0.
- Affected
- Pnggroup Libpng
gte 1.0.9, < 1.6.57..*
- Pnggroup Libpng
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Metrics
5.1
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
4.4
CVSS v3
Severity Medium on the scale from 0 to 10.
Source: SUSE, Ubuntu, BSI, CVE.org, Debian LTS, Red Hat, Debian, Msrc Update Guide, EUVD
0.2 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 9.2
Show all metrics
- Severity
- Medium
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- 38.73 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- PoC (publicly reported)
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- 5.1 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- 4.4
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- 0.2 %
- Low — model estimates < 1% exploitation likelihood.
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- 9.2
- Low — this CVE sits in the lower 10% of all CVEs scored today.
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- —
- Published
- CISA assessment (SSVC)
- Exploitation: proof of concept · not automatable · Technical impact: partial
- Source: CISA Vulnrichment, as of 9 April 2026
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-416
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- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
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- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
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
LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. From 1.0.9 to before 1.6.57, passing a pointer obtained from png_get_PLTE, png_get_tRNS, or png_get_hIST back into the corresponding setter on the same png_struct/png_info pair causes the setter to read from freed memory and copy its contents into the replacement buffer. The setter frees the internal buffer before copying from the caller-supplied pointer, which now dangles. The freed region may contain stale data (producing silently corrupted chunk metadata) or data from subsequent heap allocations (leaking unrelated heap contents into the chunk struct). This vulnerability is fixed in 1.6.57.
Source: suse_csaf, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, NVD (NIST), Debian LTS Advisories, redhat_csaf, CVE.org (MITRE), Debian Security Advisories, Microsoft Security Update Guide, cvelistv5, ENISA EUVD
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| pnggroup | libpng |
|
|
| libpng | libpng |
|
|
| Microsoft | Azure Linux |
|
|
| Open Source | libpng |
|
|
| Open Source | libpng Trunk |
|
|
Vendors and products
Affected operating systems
| Linux | debian | debian_linux | 11.0 |
| Linux | ubuntu | libpng | trusty |
| Linux | ubuntu | libpng | xenial |
| Linux | debian | libpng1.6 | bookworm |
| Linux | debian | libpng1.6 | bullseye |
| Linux | debian | libpng1.6 | trixie |
| Linux | ubuntu | libpng1.6 | bionic |
| Linux | ubuntu | libpng1.6 | focal |
| Linux | ubuntu | libpng1.6 | jammy |
| Linux | ubuntu | libpng1.6 | xenial |
Weakness classes (CWE)
CWE-416Use After Free
Variant
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Entry at MITRE CWE-416
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.
| Reference tagged as exploit | github.com (opens in a new tab) | PoC (publicly reported)reported, not verified | — |
| Reference tagged as exploit | github.com (opens in a new tab) | PoC (publicly reported)reported, not verified | — |
References & sources
- github.compnggroup/libpng/security/advisories/GHSA-6fr7-g8h7-v645x_refsource_CONFIRM, Mitigation, Patch, Vendor advisory
- github.compnggroup/libpng/issues/836x_refsource_MISC, Exploit, Issue tracking, Mitigation
- github.compnggroup/libpng/issues/837x_refsource_MISC, Exploit, Issue tracking, Mitigation
- github.compnggroup/libpng/commit/398cbe3df03f4e11bb031e07f416dfdde3684e8ax_refsource_MISC, Patch
- github.compnggroup/libpng/commit/55d20aaa322c9274491cda82c5cd4f99b48c6bccx_refsource_MISC, Patch
- lists.debian.orgdebian-lts-announce/2026/05/msg00017.htmlMailing list, Third-party advisory
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
One NVD translation into another language is hidden.
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-34757"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-34757.svg?lang=en" alt="CVE-2026-34757 – NEOSEC Intel" height="20"></a>