Advisory details:
github_osv / GHSA-ph86-p8f6-f9r2
| Advisory ID | github_osv/GHSA-ph86-p8f6-f9r2 |
| Aliases |
CVE-2026-45063
|
| Summary | Symfony Vulnerable to Identity Spoofing via Unanchored DN Regex in X509Authenticator ### Description `X509Authenticator` implements client-certificate (mTLS) authentication: the web server validates the client's certificate against a trusted CA, then passes the certificate's Subject DN (Distinguished Name: a string like `CN=Alice,O=Example,emailAddress=alice@example.com`) to Symfony via `$_SERVER['SSL_CLIENT_S_DN']`. Symfony extracts the user identifier from that string. The extraction uses an **unanchored** regex that matches `emailAddress=` anywhere in the DN string: including inside the *value* of a different RDN (Relative Distinguished Name: one `key=value` component of the DN), such as `CN`. An attacker who can obtain a certificate from a trusted CA with a free-text `CN` can smuggle `emailAddress=victim@target` inside the CN value and be authenticated as the victim. ### Resolution The `X509Authenticator` now uses a regex that anchors the match to an RDN boundary (start of string, or following a `,` / `/` separator). The patch for this issue is available [here](https://github.com/symfony/symfony/commit/ccb3f724c7ff55670a6fe3521c7bf1514cceb478) for branch 5.4. ### Credits Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 7.8 |
| Risk | 3.9 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv4 | 8.7 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-ph86-p8f6-f9r2/GHSA-ph86-p8f6-f9r2.json |
| generic_textual | HIGH |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
Vector: SSVCv2/E:N/A:N/T:T/P:M/B:A/M:M/D:T/2026-07-14T19:40:45Z/
Decision: Track
Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/45xxx/CVE-2026-45063.json
Source Advisory: vulnrichment/CVE-2026-45063
[{'Exploitation': 'none'},
{'Automatable': 'no'},
{'Technical Impact': 'total'},
{'Mission Prevalence': 'minimal'},
{'Public Well-being Impact': 'material'},
{'Mission & Well-being': 'medium'}]