On Wed, 2026-08-12 at 02:28 -0500, Junjie Cao wrote: > "Marvin" is Hubert Kario's Bleichenbacher-style timing oracle research: > > https://people.redhat.com/~hkario/marvin/ > > The affected code is the generic software RSA PKCS#1 v1.5 unpadding in > crypto/rsa-pkcs1pad.c. pkcs1pad_decrypt_complete() has three > secret-dependent early exits (leading zero byte, block type, minimum > padding length) and a loop whose trip count depends on the position of > the separator, so the time taken reveals padding validity. There is no > constant-time unpadding or implicit-rejection fallback in the tree. > > Red Hat classifies it CWE-203 and has shipped fixes only in RHEL errata > (RHSA-2024:2758, RHSA-2024:3618 and others); the bugzilla is still NEW. > Ubuntu records it unfixed upstream as of 2024-08-24 and Debian lists > src:linux vulnerable in all suites: > > https://access.redhat.com/security/cve/CVE-2023-6240 > https://ubuntu.com/security/CVE-2023-6240 > https://security-tracker.debian.org/tracker/CVE-2023-6240 > > Practical exposure is narrow: kernel PKCS#1 v1.5 use is dominated by > signature verification rather than decryption, and an attacker needs a > service driving KEYCTL_PKEY_DECRYPT with a long-lived key. The leaky > primitive is nevertheless reachable.
I'd drop this paragraph. Validating its claims would be time consuming. > > CC: Paul Barker <[email protected]> > AI-Generated: Uses Claude (claude-opus-5) > Signed-off-by: Junjie Cao <[email protected]> > --- > v3: > - drop the Marvell/s390 aside and the unrelated e8829ef1f73f paragraph > flagged in review as LLM confusion artifacts > > v2: > https://lore.kernel.org/openembedded-core/[email protected]/ > > meta/recipes-kernel/linux/cve-exclusion.inc | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/meta/recipes-kernel/linux/cve-exclusion.inc > b/meta/recipes-kernel/linux/cve-exclusion.inc > index 35e0a66..637f8b6 100644 > --- a/meta/recipes-kernel/linux/cve-exclusion.inc > +++ b/meta/recipes-kernel/linux/cve-exclusion.inc > @@ -252,3 +252,10 @@ affected fs/jfs txEnd()/lmLogClose() unmount race is > unchanged" > # > https://lore.kernel.org/linux-nvme/[email protected]/ > CVE_STATUS[CVE-2023-6238] = "unpatched: the proposed fix was applied to \ > nvme-6.6 and then reverted, no upstream fix has landed since" > + > +# "Marvin": the PKCS#1 v1.5 unpadding in crypto/rsa-pkcs1pad.c branches on > +# secret-derived data, leaking padding validity by timing. Still present in > +# mainline; fixed only in RHEL errata. > +# https://people.redhat.com/~hkario/marvin/ > +CVE_STATUS[CVE-2023-6240] = "unpatched: Bleichenbacher-style timing oracle > in \ > +crypto/rsa-pkcs1pad.c is still present in mainline, fixed only downstream in > RHEL" Recommended wording, links and include triage date: # Triaged August 2026 - "Marvin" attack, Red Hat reports this fixed but the # exact patch is unidentified (see RHSA-2024:2758, RHSA-2024:3618 & others). # Unfixed in Debian, "Needs evaluation" in Ubuntu. # https://people.redhat.com/~hkario/marvin/ # https://access.redhat.com/security/cve/cve-2023-6240 # https://security-tracker.debian.org/tracker/CVE-2023-6240 # https://ubuntu.com/security/CVE-2023-6240 CVE_STATUS[CVE-2023-6240] = "unpatched: Fixed in RHEL but patch not identified \ publicly" Best regards, -- Paul Barker
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