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CVE-2026-89541

SUNRPC: harden gss_unwrap_resp_priv length checks

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: harden gss_unwrap_resp_priv length checks gss_unwrap_resp_priv() validates the RPCSEC_GSS opaque length with offset = (u8 )(p) - (u8 )head->iov_base; if (offset + opaque_len > rcv_buf->len) goto unwrap_failed; maj_stat = gss_unwrap(ctx->gc_gss_ctx, offset, offset + opaque_len, rcv_buf); Both operands are u32 and the sum is computed in u32. A reply with opaque_len near 0xffffffff makes offset + opaque_len wrap to a small value that is below rcv_buf->len, so the bound check passes and gss_unwrap() is called with end < begin. The check also lacks a lower bound, so any opaque_len in [0, GSS_KRB5_TOK_HDR_LEN) is accepted and forwarded to gss_krb5_unwrap_v2(), whose pre-decrypt header reads at ptr+4 and ptr+6 then run past the token. A krb5p NFS server returning a crafted RPCSEC_GSS reply can drive the client into out-of-bounds reads in gss_krb5_unwrap_v2() and the rotate_left() loop that follows. Fix by replacing the single combined check with three guards that are safe in u32 arithmetic and that enforce the RFC 4121 minimum outer token length: if (offset > rcv_buf->len) goto unwrap_failed; if (opaque_len > rcv_buf->len - offset) goto unwrap_failed; if (opaque_len < GSS_KRB5_TOK_HDR_LEN) goto unwrap_failed; The first guard makes the subtraction in the second guard unconditionally safe; offset is derived from a successful xdr_inline_decode() in the head kvec, so in practice it already satisfies the bound. The floor mirrors the server-side check added in commit 5b757c2e57a5 ("SUNRPC: svcauth_gss: enforce krb5 token minimum length").

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf · fixed in 3691c4b3488d8ca046b9941e5be30c626dbbbb50; From 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf · fixed in 85fa6b12e8f439739ac36ef2aad925f37c8b976a; From 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf · fixed in 401f6a5b338d05bb1069ad814d9f77e3c367854f; From 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf · fixed in 81fd7654a8429718adfcb2a7e03496077f547ed0; From 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf · fixed in 89a15a50f84d32d4b99db86f957427fcbe20a99a; From 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf · fixed in ebcbd2523a8524c3d24e111cdbed8e271d910269; From 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf · fixed in d395c30d570ca6168f0297b191709927d1258273; From 2d2da60c63b67174add32f06e8d54c3a0c5cd9cf · fixed in 87831b92112c81db251d46756d65daa4f91af6a2

  • Linux Linux

    2.6.15

  • KernelLinux

    From 2.6.15 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 8

git.kernel.org