9.4

CVE-2026-57580: authentik: Account Takeover via SAML NameID Comment Truncation

Deferred
Published 18-08-2026Last modified 18-08-2026

Vulnerability summary

CVE-2026-57580 is a critical (CVSS 9.4) Interpretation Conflict vulnerability in goauthentik authentik. EPSS estimates a 0.59% chance of exploitation in the next 30 days, higher than 48.2% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 9.4 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
9.4/10
010
Critical · v4.0 (CVE.org)
EPSS score
0.59%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 18-08-2026
    PublishedVulnerability first disclosed.
  2. 18-08-2026
    Last modifiedVulnerability information updated.

Description

authentik is an open-source identity provider. Prior to 2026.2.6 and 2026.5.5, an inbound SAML Source configured with the non-default USERNAME_LINK or EMAIL_LINK user-matching mode interprets an XML comment in a NameID differently from the identity provider's signed assertion. An attacker with an account on the source identity provider who can set the account's NameID can inject an XML comment that truncates the value used by authentik to the text before the comment while the signed assertion remains valid. A crafted NameID can therefore truncate to a victim's username or email and bind the attacker's external identity to the victim's existing account. This grants full takeover without the victim's password or the identity provider's private key, and the malicious link persists so later logins succeed without the comment. Sources using the default unique-identifier matching mode and authentik's outbound SAML Provider role are not affected. This issue is fixed in versions 2026.2.6 and 2026.5.5.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.59%

Chance of exploitation in the next 30 days

Percentile

48%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.59% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Goauthentik1 product
  • authentik< 2026.2.6 | ≥ 2026.5.0, < 2026.5.5

1 vendor · 1 product

References

7 links