high CVSS 7.1

CVE-2021-47403·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ipack: ipoctal: fix module reference leak A reference to the carrier module was taken on every open but was only released once when the final reference to the tty struct was dropped. Fix this by taking the module reference and initialising the tty driver data when installing the tty.

Severity
high
Software
Kernel
Fixed in
5.14.10
Published
2024-05-21

Affected versions

From: 5.11

Until: 5.14.10

Fixed in: 5.14.10

How to fix this CVE

Update your Linux kernel to version 5.14.10 or later to address a module reference leak in the ipack ipoctal driver that could lead to memory exhaustion and system instability. The vulnerability allows unauthorized local users to trigger denial-of-service conditions by repeatedly opening and closing tty devices without proper reference counting. Apply the patch immediately if you are running kernel versions 5.11 through 5.14.9, particularly on systems using IndustryPack carrier hardware.

sudo dnf upgrade kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check installed kernel version by running: uname -r | awk -F. '{print $1"."$2"."$3}'
  2. Step 2: Verify if ipoctal module is loaded by running: lsmod | grep ipoctal
  3. Step 3: Monitor for device open/close patterns on ipack devices with: journalctl -u kernel | grep -i ipoctal
  4. Step 4: After updating, confirm the new kernel is active by rebooting and running: uname -r to verify version is 5.14.10 or later

FAQ

What is CVE-2021-47403?

CVE-2021-47403 is a module reference counting vulnerability in the Linux kernel's ipack ipoctal driver where each device open increments a carrier module reference counter, but the counter is only decremented once when the tty device is fully released, creating a leak that can exhaust memory.

Is CVE-2021-47403 being actively exploited?

No, CVE-2021-47403 is not currently listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available, though local attackers with user privileges can trigger the vulnerability.

What versions of Kernel are affected by CVE-2021-47403?

Kernel versions 5.11 through 5.14.9 are vulnerable; version 5.14.10 and later contain the fix.

How do I check if my server is vulnerable to CVE-2021-47403?

Run 'uname -r' to check your kernel version; if it reports 5.11.x through 5.14.9, and 'lsmod | grep ipoctal' shows the module is loaded, your system is vulnerable.

Does Defensia detect CVE-2021-47403?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2021-47403 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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