high CVSS 7.8

CVE-2023-52775·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net/smc: avoid data corruption caused by decline We found a data corruption issue during testing of SMC-R on Redis applications. The benchmark has a low probability of reporting a strange error as shown below. "Error: Protocol error, got "\xe2" as reply type byte" Finally, we found that the retrieved error data was as follows: 0xE2 0xD4 0xC3 0xD9 0x04 0x00 0x2C 0x20 0xA6 0x56 0x00 0x16 0x3E 0x0C 0xCB 0x04 0x02 0x01 0x00 0x00 0x20 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xE2 It is quite obvious that this is a SMC DECLINE message, which means that the applications received SMC protocol message. We found that this was caused by the following situations: client server ¦ clc proposal -------------> ¦ clc accept <------------- ¦ clc confirm -------------> wait llc confirm send llc confirm ¦failed llc confirm ¦ x------ (after 2s)timeout wait llc confirm rsp wait decline (after 1s) timeout (after 2s) timeout ¦ decline --------------> ¦ decline <-------------- As a result, a decline message was sent in the implementation, and this message was read from TCP by the already-fallback connection. This patch double the client timeout as 2x of the server value, With this simple change, the Decline messages should never cross or collide (during Confirm link timeout). This issue requires an immediate solution, since the protocol updates involve a more long-term solution.

Severity
high
Software
Kernel
Fixed in
6.6.4
Published
2024-05-21

Affected versions

From: 6.2

Until: 6.6.4

Fixed in: 6.6.4

How to fix this CVE

Update your Linux kernel to version 6.6.4 or later to resolve a critical SMC (Shared Memory Communications) protocol issue that causes data corruption when connection negotiation times misalign between client and server. This vulnerability affects systems using SMC-R for network communication, particularly in Redis and similar applications. Apply the kernel update immediately and reboot your system to activate the patched version.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check your current kernel version: uname -r
  2. Verify if SMC (CONFIG_SMC) is enabled: grep CONFIG_SMC /boot/config-$(uname -r)
  3. Review system logs for SMC protocol errors: journalctl -u kernel -g 'smc\|decline' | head -20
  4. Confirm the fix is applied by verifying kernel version is 6.6.4 or later: uname -r | grep -E '6\.[6-9]|[7-9]\.[0-9]'
  5. For SMC-specific validation, check dmesg for SMC connection timeouts: dmesg | grep -i 'smc.*timeout\|smc.*decline'

FAQ

What is CVE-2023-52775?

This vulnerability involves a timing race condition in Linux kernel's SMC protocol implementation where decline messages can be received as application data, causing protocol corruption. Applications receive raw SMC control frames instead of expected payload, manifesting as protocol errors in services like Redis.

Is CVE-2023-52775 being actively exploited?

No, this CVE is not listed on the CISA KEV catalog and has no known public exploits. However, it poses significant risk to production systems running SMC-R based workloads due to data corruption potential.

What versions of Kernel are affected by CVE-2023-52775?

Linux kernel versions 6.2 through 6.6.3 are vulnerable. The fix is included in kernel 6.6.4 and all subsequent releases.

How do I check if my server is vulnerable to CVE-2023-52775?

Run 'uname -r' to check your kernel version. If the output shows version 6.2 to 6.6.3 AND 'grep CONFIG_SMC /boot/config-$(uname -r)' returns 'CONFIG_SMC=y', your system is vulnerable.

Does Defensia detect CVE-2023-52775?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel package is installed on a monitored server within the vulnerable range, CVE-2023-52775 will appear in your dashboard with remediation steps.

Related Kernel CVEs

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CVE-2026-52986CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_sip: don't use simple_strtoul Replace unsafe port parsing in epaddr_len(), ct_sip_parse_header_uri(), and ct_sip_parse_request() with a new sip_parse_port() helper that validates each digit against the buffer limit, eliminating the use of simple_strtoul() which assumes NUL-terminated strings. The previous code dereferenced pointers without bounds checks after sip_parse_addr() and relied on simple_strtoul() on non-NUL-terminated skb data. A port that reaches the buffer limit without a trailing character is also rejected as malformed. Also get rid of all simple_strtoul() usage in conntrack, prefer a stricter version instead. There are intentional changes: - Bail out if number is > UINT_MAX and indicate a failure, same for too long sequences. While we do accept 05535 as port 5535, we will not accept e.g. 'sip:10.0.0.1:005060'. While its syntactically valid under RFC 3261, we should restrict this to not waste cycles when presented with malformed packets with 64k '0' characters. - Force base 10 in ct_sip_parse_numerical_param(). This is used to fetch 'expire=' and 'rports='; both are expected to use base-10. - In nf_nat_sip.c, only accept the parsed value if its within the 1k-64k range. - epaddr_len now returns 0 if the port is invalid, as it already does for invalid ip addresses. This is intentional. nf_conntrack_sip performs lots of guesswork to find the right parts of the message to parse. Being stricter could break existing setups. Connection tracking helpers are designed to allow traffic to pass, not to block it. Based on an earlier patch from Jenny Guanni Qu <qguanni@gmail.com>.
CVE-2026-63993CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.
CVE-2026-64046CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: net: tls: prevent chain-after-chain in plain text SG Sashiko points out that if end = 0 (start != 0) the current code will create a chain link to content type right after the wrap link: This would create a chain where the wrap link points directly to another chain link. The scatterlist API sg_next iterator does not recursively resolve consecutive chain links. meaning this is illegal input to crypto. The wrapping link is unnecessary if end = 0. end is the entry after the last one used so end = 0 means there's nothing pushed after the wrap: end start i v v v [ ]...[ ][ d ][ d ][ d ][ d ][rsv for wrap] Skip the wrapping in this case. TLS 1.3 can use the "wrapping slot" for it's chaining if end = 0. This avoids the chain-after-chain. Move the wrap chaining before marking END and chaining off content type, that feels like more logical ordering to me, but should not matter from functional perspective.
CVE-2026-64055CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: net: ethernet: cortina: Carry over frag counter The gmac_rx() NAPI poll function assembles packets in an SKB from a ring buffer. If the ring buffer gets completely emptied during a poll cycle, we exit gmac_rx(), but the packet is not yet completely assembled in the SKB, yet the fragment counter frag_nr is reset to zero on the next invocation. Solve this by making the RX fragment counter a part of the port struct, and carry it over between invocations. Reset the fragment counter only right after calling napi_gro_frags(), on error (after calling napi_free_frags()) or if stopping the port. Reset it in some place where not strictly necessary just to emphasize what is going on. This was found by Sashiko during normal patch review.

References

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