Heap-based Buffer Overflow in Git
- Exploited
- No known exploitation
- Fix
- Fixed in 2.49.1, 2.50.2, 2.51.3, 2.52.1, 2.53.1, and 3 more
- Who is exposed
- Specific setups only
Do first: Upgrade to a fixed version: 2.49.1, 2.50.2, 2.51.3, 2.52.1, 2.53.1, or one of 3 more.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 20/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Affected versions of Git contain a heap-based buffer overflow in its three-way merge code that can be triggered remotely, without logging in, through a repository an attacker controls, though it requires a user to take an action such as running a merge or rebase. The overflow can crash Git and may allow heap corruption with attacker-influenced data.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original 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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure12/25Specific setups only, reachable over the network without a login
- Reach?/20Unknown. No tracked technology or package matched
- Severity7.5/10CVSS 7.5
- No patch0/5No signal
What would change the score
- Would score about 70 if added to CISA KEV
- Would score about 65 if CISA's SSVC rates exploitation active
What to do
Upgrade to a fixed version: 2.49.1, 2.50.2, 2.51.3, 2.52.1, 2.53.1, or one of 3 more.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-105437 (Heap-based Buffer Overflow in Git), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-105437 (entry last updated 2026-11-10): Affected: - Git Git: fixed in 2.49.1; from 2.50.0-rc0, fixed in 2.50.2; from 2.51.0-rc0, fixed in 2.51.3; from 2.52.0-rc0, fixed in 2.52.1; from 2.53.0-rc0, fixed in 2.53.1; from 2.54.0-rc0, fixed in 2.54.1; from 2.55.0-rc0, fixed in 2.55.1; from 2.56.0-rc0, fixed in 2.56.1 Fixed versions: 2.49.1, 2.50.2, 2.51.3, 2.52.1, 2.53.1, 2.54.1, 2.55.1, 2.56.1. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. Attacker needs: network access, no login, a user action. CISA KEV: CVE-2026-105437 is not listed as of cve.now's last read. This KEV status is for CVE-2026-105437 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://gitlab.com/gitlab-org/git/-/work_items/814 - https://gitlab.com/gitlab-org/gitlab/-/work_items/632121 - https://www.cve.org/CVERecord?id=CVE-2026-105437 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-105437 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-105437.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- Git Git
fixed in 2.49.1; From 2.50.0-rc0 · fixed in 2.50.2; From 2.51.0-rc0 · fixed in 2.51.3; From 2.52.0-rc0 · fixed in 2.52.1; From 2.53.0-rc0 · fixed in 2.53.1; From 2.54.0-rc0 · fixed in 2.54.1; From 2.55.0-rc0 · fixed in 2.55.1; From 2.56.0-rc0 · fixed in 2.56.1
Evidence 5
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Public exploit code · 1
Establishes: Public exploit code exists (Exploit-DB, Metasploit, Nuclei and GitHub).
- Exploit
Corrections
None so far.
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Questions about CVE-2026-105437
Is CVE-2026-105437 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-105437?
Git: before 2.49.1; from 2.50.0-rc0 before 2.50.2; from 2.51.0-rc0 before 2.51.3; from 2.52.0-rc0 before 2.52.1; from 2.53.0-rc0 before 2.53.1; from 2.54.0-rc0 before 2.54.1; from 2.55.0-rc0 before 2.55.1; from 2.56.0-rc0 before 2.56.1.Source: cve.now feed data
How do I fix CVE-2026-105437?
Upgrade to the fixed release for your version line: 2.50.2, 2.51.3, 2.52.1, 2.53.1, 2.54.1, 2.55.1, or 2.56.1 or later. The advisory's quoted fix instruction is 'Upgrade to versions 2.50.2, 2.51.3, 2.52.1, 2.53.1, 2.54.1, 2.55.1, 2.56.1 or above.' The affected ranges list versions before 2.49.1 as fixed in 2.49.1.Source: cve.org