Gitea SSH Key Parser Denial of Service (CVE-2026-56657)
Gitea versions prior to 1.27.0 have a denial of service vulnerability in the SSH key ingestion endpoint. The flaw is due to an O(N²) string concatenation loop in the SSH2 key normalization function that lacks input size limits. An authenticated user can submit a maliciously large SSH2 formatted key, causing excessive CPU and memory usage that may take the server offline. This vulnerability is identified as CVE-2026-56657 and is classified as a moderate severity issue. A patch is available to address this vulnerability.
AI Analysis
Technical Summary
CVE-2026-56657 affects Gitea versions before 1.27.0 and involves a denial of service vulnerability triggered by the SSH key ingestion endpoint. The root cause is an inefficient O(N²) string concatenation loop in the SSH2 key normalization function, which does not impose limits on input size. An authenticated attacker can exploit this by submitting a large RFC 4716 (SSH2) formatted SSH key, leading to excessive CPU and memory consumption that can disrupt service availability. The vulnerability is categorized under CWE-400 (Uncontrolled Resource Consumption). A patch is available to fix this issue.
Potential Impact
Exploitation of this vulnerability allows an authenticated user to cause denial of service by overwhelming the server's CPU and memory resources through a specially crafted large SSH2 key. This can result in the server becoming unresponsive or offline, impacting availability of the Gitea service.
Mitigation Recommendations
A patch is available for this vulnerability. Users should upgrade to Gitea version 1.27.0 or later to remediate the issue. Until patched, restricting access to the SSH key ingestion endpoint to trusted users and monitoring for unusual resource consumption may help mitigate risk.
Gitea SSH Key Parser Denial of Service (CVE-2026-56657)
Description
Gitea versions prior to 1.27.0 have a denial of service vulnerability in the SSH key ingestion endpoint. The flaw is due to an O(N²) string concatenation loop in the SSH2 key normalization function that lacks input size limits. An authenticated user can submit a maliciously large SSH2 formatted key, causing excessive CPU and memory usage that may take the server offline. This vulnerability is identified as CVE-2026-56657 and is classified as a moderate severity issue. A patch is available to address this vulnerability.
CVSS v4.0
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-56657 affects Gitea versions before 1.27.0 and involves a denial of service vulnerability triggered by the SSH key ingestion endpoint. The root cause is an inefficient O(N²) string concatenation loop in the SSH2 key normalization function, which does not impose limits on input size. An authenticated attacker can exploit this by submitting a large RFC 4716 (SSH2) formatted SSH key, leading to excessive CPU and memory consumption that can disrupt service availability. The vulnerability is categorized under CWE-400 (Uncontrolled Resource Consumption). A patch is available to fix this issue.
Potential Impact
Exploitation of this vulnerability allows an authenticated user to cause denial of service by overwhelming the server's CPU and memory resources through a specially crafted large SSH2 key. This can result in the server becoming unresponsive or offline, impacting availability of the Gitea service.
Mitigation Recommendations
A patch is available for this vulnerability. Users should upgrade to Gitea version 1.27.0 or later to remediate the issue. Until patched, restricting access to the SSH key ingestion endpoint to trusted users and monitoring for unusual resource consumption may help mitigate risk.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-4xjf-493q-98p3
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-56657"]
- Ecosystems
- ["Go"]
- Database Specific Severity
- MODERATE
- Cvss Version
- 4.0
Threat ID: 6a600ab09c2644c7f8fe1a46
Added to database: 07/22/2026, 00:11:28 UTC
Last enriched: 08/14/2026, 12:55:07 UTC
Last updated: 09/14/2026, 22:01:35 UTC
Views: 25
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