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CVE PROGRAM SOURCE RECORD9.8 Critical

CVE-2026-89550

SUNRPC: svcauth_gss: enforce krb5 token minimum length

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: svcauth_gss: enforce krb5 token minimum length svcauth_gss_unwrap_priv() validates only an upper bound on the wire-supplied opaque length before handing the buffer to gss_unwrap(): if (len > xdr_stream_remaining(xdr)) goto unwrap_failed; offset = xdr_stream_pos(xdr); ... maj_stat = gss_unwrap(ctx, offset, offset + len, buf); The wire value `len` flows unchanged as the upper bound into the krb5 unwrap path, so a len in [0, 16] passes this check and is handed to gss_unwrap(). For a krb5 v2 context that lands in gss_krb5_unwrap_v2(), which reads the 16-byte RFC 4121 token header fields at ptr+4 and ptr+6 and then calls rotate_left() before any integrity check. With a sub-header length the header reads run past the token, and _rotate_left()'s `shift %= buf->len` path can divide by zero when buf->len has been driven to zero by the truncated token. A header-only token (len == 16) is equally invalid: with a non-zero RRC field and the opaque blob ending at the XDR buffer boundary, rotate_left() builds a zero-length subbuffer, reaching the same division. Reject the token at the server entry point before it reaches the krb5 unwrap core. A valid sealed RFC 4121 token must contain the 16-byte header plus at least some encrypted payload. Fix by adding a minimum-length check immediately after the existing upper-bound check: if (len <= GSS_KRB5_TOK_HDR_LEN) goto unwrap_failed;

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 7c9fdcfb1b64c47ed618c103b617af3f86e1239c to < 2188232509f1559cb8fcb0c9a4b1e04317fa0f15affected
  • 7c9fdcfb1b64c47ed618c103b617af3f86e1239c to < 0ea5b0c7f212c2772d32c2b88287b89a9cdf6eddaffected
  • 7c9fdcfb1b64c47ed618c103b617af3f86e1239c to < dd6afc6cab8c5d387d1ed2f069562ef7bdadd651affected
  • 7c9fdcfb1b64c47ed618c103b617af3f86e1239c to < de942dd8c2c8358bcad04ce44271954c48924423affected
  • 7c9fdcfb1b64c47ed618c103b617af3f86e1239c to < 2eed1e6a976a44015c3ee78841fe336796e2b21caffected
  • 7c9fdcfb1b64c47ed618c103b617af3f86e1239c to < a919c5c88769cf8fb3ec071e6078d830bf512489affected

Linux Linux

Default version status: affected

  • 2.6.18affected
  • 0 to < 2.6.18unaffected
  • 6.1.191 to ≤ 6.1.*unaffected
  • 6.6.157 to ≤ 6.6.*unaffected
  • 6.12.109 to ≤ 6.12.*unaffected
  • 6.18.50 to ≤ 6.18.*unaffected
  • 7.2.4 to ≤ 7.2.*unaffected
  • 7.3 to ≤ *unaffected

References