MediumCVE-2026-105437

Git: Heap-based Buffer Overflow (CVE-2026-105437)

Published 13.11.2026Sources: BSI

Public exploit

What is affected, what to do

An exploit is publicly available. Update Git to version 2.49.1, Git to version 2.50.2, Git to version 2.51.3.

Affected: Git lt *..2.49.1
Git lt 2.50.0-rc0..2.50.2
Git lt 2.51.0-rc0..2.51.3
Git lt 2.52.0-rc0..2.52.1
Git lt 2.53.0-rc0..2.53.1
Git lt 2.54.0-rc0..2.54.1
Git lt 2.55.0-rc0..2.55.1
Git lt 2.56.0-rc0..2.56.1
Fixed in: Git 2.49.1
Git 2.50.2
Git 2.51.3
Git 2.52.1
Git 2.53.1
Git 2.54.1
Git 2.55.1
Git 2.56.1

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

Metrics

6.4

XIEM Effective CVSS

Highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v3

6.4

CVSS v3

Severity Medium on the scale from 0 to 10.

Source: BSI

0.4 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 34.7

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: 71.64 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: 6.4 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: 6.4
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: 0.4 %; 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: 34.7; Elevated — this CVE ranks above at least 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: 13.11.2026
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-122

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

Affected versions of Git have a heap buffer overflow in the three-way merge code (xdiff), which an attacker can trigger through a repository they control.

When Git merges a file, it first adds up the size of the merged output, allocates a buffer of that size, and then writes the output into it. That total was kept in a 32-bit signed integer. The conflict-marker-size attribute, which can be set from a committed .gitattributes file, accepts any positive integer, and the markers are written several times for every conflict. A small file with a huge marker size and many separate conflicts can therefore push the total past 4 GiB, so the integer wraps to a small value and Git writes attacker-controlled merge output past the end of a buffer that is too small. At minimum this crashes Git, and because the overflow is large and its contents are largely attacker-controlled, worse heap corruption is possible.

Any command that does a textual three-way merge can trigger it, such as git-merge(1), git-rebase(1), git-cherry-pick(1), and git-merge-tree(1). The latter is most likely a target for Git forges, which might use git-merge-tree(1) on the server-side to check mergeability. When the server reads attributes from trees in the repository (for example through attr.tree or --attr-source), any user who can push branches and request that they be merged (for example by opening a pull or merge request) can trigger the overflow without anyone else doing anything, and the data they push is small because the oversized output only appears during the merge.

The problem has been patched by computing the size as size_t and checking every addition for overflow, so Git stops with an error instead of overflowing.

Servers that cannot upgrade right away can add

conflict-marker-size=7

to each repository's info/attributes as a workaround, which overrides any in-tree .gitattributes, or turn off server-side mergeability checks for untrusted repositories.

Source: BSI WID Portal

Affected products

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

Affected products
		Affected versions	Fixed in
Git	Git	`2.50.0-rc0 – < 2.50.2` `2.51.0-rc0 – < 2.51.3` `2.52.0-rc0 – < 2.52.1` `2.53.0-rc0 – < 2.53.1` `2.54.0-rc0 – < 2.54.1` `2.55.0-rc0 – < 2.55.1` `2.56.0-rc0 – < 2.56.1` `< 2.49.1`	`2.50.2` `2.51.3` `2.52.1` `2.53.1` `2.54.1` `2.55.1` `2.56.1` `2.49.1`
Open Source	git	`< 2.56.1`	`2.56.1`
Open Source	GitLab	`< 19.3.8` `< 19.4.6` `< 19.5.4`	`19.3.8` `19.4.6` `19.5.4`

Vendors and products

Affected operating systems

Affected operating systems

Other	Sonstiges	—
Linux	UNIX	—
Windows	Windows	—

Weakness classes (CWE)

CWE-122Heap-based Buffer Overflow
Variant
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Entry at MITRE CWE-122

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

Reference tagged as exploit	hackerone.com (opens in a new tab)	PoC (publicly reported)reported, not verified	—

References & sources

docs.gitlab.comGitLab Critical Patch Release vom 2026-11-10BSI
CVE.org (MITRE)CVE Record vom 2026-11-10BSI
security.gentoo.orgGentoo Linux Security Advisory GLSA-202611-02 vom 2026-11-11BSI
gitlab.comgitlab-org/git/-/work_items/814euvd
gitlab.comgitlab-org/gitlab/-/work_items/632121euvd
hackerone.comHackerOne Bug Bounty Report #4044249euvd, Technical description, Exploit, Permissions required
NVD (NIST)vuln/detail/CVE-2026-105437euvd

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).

10.11.2026ReceivedGitLab

CVSS V3.1: AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Weakness type: CWE-122

Description added or changed

New references:

Show 7 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	Affected versions of Git have a heap buffer overflow in the three-way merge code (xdiff), which an attacker can trigger through a repository they control. When Git merges a file, it first adds up the size of the merged output, allocates a buffer of that size, and then writes the output into it. That total was kept in a 32-bit signed integer. The conflict-marker-size attribute, which can be set from a committed .gitattributes file, accepts any positive integer, and the markers are written several times for every conflict. A small file with a huge marker size and many separate conflicts can therefore push the total past 4 GiB, so the integer wraps to a small value and Git writes attacker-controlled merge output past the end of a buffer that is too small. At minimum this crashes Git, and because the overflow is large and its contents are largely attacker-controlled, worse heap corruption is possible. Any command that does a textual three-way merge can trigger it, such as git-merge(1), git-rebase(1), git-cherry-pick(1), and git-merge-tree(1). The latter is most likely a target for Git forges, which might use git-merge-tree(1) on the server-side to check mergeability. When the server reads attributes from trees in the repository (for example through attr.tree or --attr-source), any user who can push branches and request that they be merged (for example by opening a pull or merge request) can trigger the overflow without anyone else doing anything, and the data they push is small because the oversized output only appears during the merge. The problem has been patched by computing the size as size_t and checking every addition for overflow, so Git stops with an error instead of overflowing. Servers that cannot upgrade right away can add * conflict-marker-size=7 to each repository's info/attributes as a workaround, which overrides any in-tree .gitattributes, or turn off server-side mergeability checks for untrusted repositories.
CVSS	added	—	AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness type (CWE)	added	—	CWE-122
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/105xxx/CVE-2026-105437.json">CVE-2026-105437</a>
Reference	added	—	https://gitlab.com/gitlab-org/git/-/work_items/814
Reference	added	—	https://gitlab.com/gitlab-org/gitlab/-/work_items/632121
Reference	added	—	https://hackerone.com/reports/4044249

Source identifier: cve@gitlab.com

Linked CVEs

Linked CVEs

Medium	CVE-2026-105437	Heap-based Buffer Overflow in Git	6.4	—

Embed badge

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

<a href="https://intel.neosec.eu/en/cve/CVE-2026-105437"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-105437.svg?lang=en" alt="CVE-2026-105437 – NEOSEC Intel" height="20"></a>