CVE-2026-31649 — CVE & Security Advisory Radar

🎯 CVE-2026-31649 🇪🇺 EUVD

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CVE-2026-31649 | In the Linux kernel, the following vulnerability has been resolved: net: stmmac: fix integer underflow in chain mode The jumbo_frm() chain-mode implementation unconditionally computes len = nopaged_len - bmax; where nopaged_len = skb_headlen(skb) (linear bytes only) and bmax is BUF_SIZE_8KiB or BUF_SIZE_2KiB. However, the caller stmmac_xmit() decides to invoke jumbo_frm() based on skb->len (total length including page fragments): is_jumbo = stmm

In the Linux kernel, the following vulnerability has been resolved:

net: stmmac: fix integer underflow in chain mode

The jumbo_frm() chain-mode implementation unconditionally computes

len = nopaged_len - bmax;

where nopaged_len = skb_headlen(skb) (linear bytes only) and bmax is
BUF_SIZE_8KiB or BUF_SIZE_2KiB. However, the caller stmmac_xmit()
decides to invoke jumbo_frm() based on skb->len (total length including
page fragments):

is_jumbo = stmmac_is_jumbo_frm(priv, skb->len, enh_desc);

When a packet has a small linear portion (nopaged_len len > bmax), the
subtraction wraps as an unsigned integer, producing a huge len value
(~0xFFFFxxxx). This causes the while (len != 0) loop to execute
hundreds of thousands of iterations, passing skb->data + bmax * i
pointers far beyond the skb buffer to dma_map_single(). On IOMMU-less
SoCs (the typical deployment for stmmac), this maps arbitrary kernel
memory to the DMA engine, constituting a kernel memory disclosure and
potential memory corruption from hardware.

Fix this by introducing a buf_len local variable clamped to
min(nopaged_len, bmax). Computing len = nopaged_len - buf_len is then
always safe: it is zero when the linear portion fits within a single
descriptor, causing the while (len != 0) loop to be skipped naturally,
and the fragment loop in stmmac_xmit() handles page fragments afterward.

Klassifikation & Betroffenheit:

Linux Linux patch: 6.6.135Linux 286a837217204b1ef105e3a554d0757e4fdfaac1 <b7b8012193fd98236d7ae05d4b553f010a77b2efLinux patch: 5.10.253Linux 286a837217204b1ef105e3a554d0757e4fdfaac1 <51f4e090b9f87b40c21b6daadb5c06e6c0a07b67Linux 286a837217204b1ef105e3a554d0757e4fdfaac1 <513e06735f5be575b409d195822195348b164e48Linux 286a837217204b1ef105e3a554d0757e4fdfaac1 <275bdf762e82082f064e60a92448fa2ac43cf95bLinux patch: 6.1.169Linux patch: 6.12.82

Improper Restriction of Operations within the Bounds of a Memory Buffer 🎯 High

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

🛡️ Empfohlene Mitigation: Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow prot…

Vollständige Definition bei MITRE ➔

⚔️ Typische Angriffsmuster (CAPEC):

CAPEC-10 · Buffer Overflow via Environment Variable… (High) CAPEC-14 · Client-side Injection-induced Buffer Ove… (High) CAPEC-24 · Filter Failure through Buffer Overflow (High) CAPEC-42 · MIME Conversion (High) CAPEC-44 · Overflow Binary Resource File (Very High) CAPEC-45 · Buffer Overflow via Symbolic Links (High) CAPEC-100 · Overflow Buffers (Very High) CAPEC-123 · Buffer Manipulation (Very High)

🧩 Ähnliche Schwachstellen (Hersteller/Klasse/Score-Band):

CVE-2026-74705 10.0 CVE-2026-74612 10.0 CVE-2026-74475 10.0 CVE-2026-74309 10.0 CVE-2026-74280 10.0

🩹 Patch verfügbar (OSV):

🩹 Kernel ≥ 5.10.253 🩹 Kernel ≥ 5.15.203 🩹 Kernel ≥ 6.1.169 🩹 Kernel ≥ 6.6.135 🩹 Kernel ≥ 6.12.82 🩹 Kernel ≥ 6.18.23

📚 Referenzen & Quellen:

🇪🇺 Original-Eintrag (ENISA EUVD) 🇺🇸 NVD-Eintrag

Ausnutzungs-Zeitleiste:

Reserviert 2026

Veröffentlicht 04/2026

Heute 17.09.

CVSS-Vektor-Analyse: 9.8

AV · Angriffsvektor Netzwerk

AC · Komplexität Gering

PR · Privilegien Keine

UI · Interaktion Keine

S · Scope Unverändert

C · Vertraulichkeit Hoch

I · Integrität Hoch

A · Verfügbarkeit Hoch

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Veröffentlicht:24.04.2026

Aktualisiert:14.07.2026 13:18

Assigner (CNA):Linux

EUVD-ID:EUVD-2026-25542

Quellen: 🇪🇺 EUVD-Datenbank (ENISA) + 🇺🇸 NVD-Anreicherung · 24-h-Cache

CWE-119: Memory Corruption ✓ Offizieller Patch / Advisory verfügbar

💡 Gegenmaßnahme: Kernel-Paket aktualisieren (apt upgrade linux-image / yum update kernel) und System neu starten.

Tier	2026-08-29	2026-09-17
≥90 %	4	0
≥50 %	4	0
≥10 %	3	0
<10 %	304	300

9.8 CRITICAL

🇪🇺 EUVD

EPSS

46%

CVE-2026-31649 🌐 Netzwerk (Remote) 🔓 Keine Authentifizierung nötig

Linux

CVE-2026-31649 | In the Linux kernel, the following vulnerability has been resolved: net: stmmac: fix integer underflow in chain mode The jumbo_frm() chain-mode implementation unconditionally computes len = nopaged_len - bmax; where nopaged_len = skb_headlen(skb) (linear bytes only) and bmax is BUF_SIZE_8KiB or BUF_SIZE_2KiB. However, the caller stmmac_xmit() decides to invoke jumbo_frm() based on skb->len (total length including page fragments): is_jumbo = stmm

CWE-119: Memory Corruption ✓ Offizieller Patch / Advisory verfügbar

💡 Gegenmaßnahme: Kernel-Paket aktualisieren (apt upgrade linux-image / yum update kernel) und System neu starten.

24.04.2026

🛡️ Details ➔

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