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CVE-2026-89550— SUNRPC: svcauth_gss: enforce krb5 token minimum length

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于svcauth_gss_unwrap_priv()仅验证上层长度边界而未校验krb5令牌最小长度，导致截断令牌进入gss_krb5_unwrap_v2()后头部读取越界，_rotate_left()的取模操作可能被零长度缓冲区触发除零，造成系统崩溃。

CVSS 9.8 · Critical EPSS 0.46% · P39

Possible ATT&CK Techniques 1 AI

T1598 · Phishing for Information

Affected Version Matrix 12

VendorProduct Version RangeStatus
Linux Linux 7c9fdcfb1b64c47ed618c103b617af3f86e1239c< 0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd affected
7c9fdcfb1b64c47ed618c103b617af3f86e1239c< dd6afc6cab8c5d387d1ed2f069562ef7bdadd651 affected
7c9fdcfb1b64c47ed618c103b617af3f86e1239c< de942dd8c2c8358bcad04ce44271954c48924423 affected
7c9fdcfb1b64c47ed618c103b617af3f86e1239c< 2eed1e6a976a44015c3ee78841fe336796e2b21c affected
7c9fdcfb1b64c47ed618c103b617af3f86e1239c< a919c5c88769cf8fb3ec071e6078d830bf512489 affected
2.6.18 affected
< 2.6.18 unaffected
6.6.157≤ 6.6.* unaffected
… +4 more rows
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I. Basic Information for CVE-2026-89550

Vulnerability Information
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Vulnerability Title
SUNRPC: svcauth_gss: enforce krb5 token minimum length
Source: CVE Program / CVE List V5
Vulnerability 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;
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel存在安全漏洞，该漏洞源于svcauth_gss_unwrap_priv()仅验证上层长度边界而未校验krb5令牌最小长度，导致截断令牌进入gss_krb5_unwrap_v2()后头部读取越界，_rotate_left()的取模操作可能被零长度缓冲区触发除零，造成系统崩溃。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 7c9fdcfb1b64c47ed618c103b617af3f86e1239c ~ 0ea5b0c7f212c2772d32c2b88287b89a9cdf6edd -
Linux Linux 2.6.18 -

II. Public POCs for CVE-2026-89550

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III. Intelligence Information for CVE-2026-89550

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Patches & Fixes for CVE-2026-89550 (3)

Vendor Advisories for CVE-2026-89550 (1)

Other References for CVE-2026-89550 (1)

Same Patch Batch · Linux · 2026-09-11 · 431 CVEs total

CVE-2026-89688 9.8 CRITICAL nfsd: drop the stateid, not the stateowner, on seqid_op replay retry
CVE-2026-89655 9.8 CRITICAL ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock
CVE-2026-89658 9.8 CRITICAL NFSD: Prevent client use-after-free during NFSv4.0 revoked-state cleanup
CVE-2026-89660 9.8 CRITICAL NFSD: Prevent client use-after-free during admin state revocation
CVE-2026-89659 9.8 CRITICAL NFSD: Prevent client use-after-free during delegation revoke
CVE-2026-89662 9.8 CRITICAL NFSD: Prevent lock owner use-after-free during client teardown
CVE-2026-89669 9.8 CRITICAL nfsd: initialize copy-notify stateid before publishing it
CVE-2026-89674 9.8 CRITICAL nfsd: fix XDR length calculation in nfsd4_ff_encode_layoutget
CVE-2026-89675 9.8 CRITICAL nfsd: fix UAF in async copy cancel and shutdown
CVE-2026-89676 9.8 CRITICAL nfsd: fix stale s2s_cp_stateids IDR entry for async COPY
CVE-2026-89677 9.8 CRITICAL nfsd: fix possible fh_compose of wrong dentry in nfsd4_create_file()
CVE-2026-89681 9.8 CRITICAL nfsd: fix layout fence worker double-reference race
CVE-2026-89686 9.8 CRITICAL nfsd: fix BUG_ON in nfsd4_alloc_layout_stateid on racing delegation revoke
CVE-2026-89703 9.8 CRITICAL nfsd: set SC_STATUS_FREED in nfsd4_drop_revoked_stid for delegations
CVE-2026-89479 9.8 CRITICAL sctp: stop processing a packet once its association is deleted
CVE-2026-89478 9.8 CRITICAL sctp: drop a chunk if its transport was removed
CVE-2026-89702 9.8 CRITICAL nfsd: size fh_verify server sockaddr slot by xpt_locallen
CVE-2026-89482 9.8 CRITICAL nvme-tcp: do not accept C2HData based on blk_rq_payload_bytes() alone
CVE-2026-89708 9.8 CRITICAL nfsd: RCU-protect cl_cb_session to fix use-after-free on session teardown
CVE-2026-89712 9.8 CRITICAL NFSD: restart ssc_expire_umount walk after dropping nfsd_ssc_lock

Showing top 20 of 431 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

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Same vendor: Linux

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