EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
- •High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 7.5Exploit: None knownExposed services: Not assessed
A fix is available — apply it.
Fixed versions, as the CVE record's CNA (GitLab Inc.) states them: "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."
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.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from Vulnrichment. EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it